Project Summary The public health and economic impact of circadian and sleep misalignment had grown enormously with the increasingly global and 24 hour nature of our society, and costs are in the billions. In spite of this, however, we know very little about the mechanisms by which sleep and the circadian clock influence memory circuits. Memory formation is bidirectionally sensitive to sleep levels. Sleep in the temporal window following training can enhance formation of memory, while sleep deprivation has negative effects on its formation. In Drosophila, we have a very detailed understanding both of the processes that underlie memory formation and of the circadian clock and sleep circuits. In this proposal we will leverage this knowledge to understand, for the first time at a cellular level, the direct links between memory and sleep/circadian systems. In Aim 1 we demonstrate that the fly circadian circuit and the fly memory circuits have direct anatomical connections. Further, we show that a circadian neuropeptide which has been associated with arousal is required for normal memory. We hypothesize that these connections provide the pro- arousal function of the circadian clock that helps maintain cognitive function over the course of the day. We will investigate the molecular function of the connections between these peptidergic clock cells and memory circuits and their behavioral role. Understanding connectivity of the clock and associative memory processes at this level will provide us with the ability to develop novel cognitive protection and enhancement strategies. In Aim 2 we demonstrate that the very process that underlies formation of stable associative memory, concurrent activation of neurons that drive memory consolidation, also drives sleep. This sleep is tightly linked to the learning process and we hypothesize that it is critical for consolidation. We will define the molecular and cellular processes that cause sleep and consolidation in this circuit and investigate the role of concurrently generated sleep in behavior. Understanding this linkage will provide important insight into how manipulation of sleep can be used to enhance memory formation.